Good morning,
just starting with the awesome d3js library ...
I want to show only a portion of a graph with the force directed layout. The idea is to have one node declared as the "center" and show all nodes within a distance of two (for example) from this center node, the neighbors of the center node and the neighbors of the neighbors. If the user clicks on one of the displayed nodes it becomes the "new" center node and a different "subgraph" is displayed. I wonder if there is an example around implementing this kind of subgraph layout and if some kind of a "node-distance" algorithm is already implemented in d3js.
Thanks a lot
martin
UPDATE:
Just found the example Modifying a Force Layout which illuminates how to add and remove nodes and edges from a force directed layout.
I just uploaded a "proof of concept level" of an interactive force directed subgraph.
http://justdharma.com/d3/sub-graph/
In this example I use backbonejs under the hood. Being the first time I implement something with backbonejs, I for sure use it in a very crude manner. While this example might illuminate one way how an interactive sub-graph can be achieved it is for sure not a template how to do it - as said just a proof of concept hack ...
This isn't implemented in D3, and I'm not aware of any examples. What you would have to do is the following:
Set the fixed attribute of the new center node to true to prevent the force layout from changing its position.
Set the px and py attributes of that same node to the center position.
For each node in your force layout, compute the shortest path to the new center node.
Depending on the length of the path in each case, either remove the node or keep it.
The trickiest part here is the computation of the path from each node to the new center, but even this is a pretty standard algorithmic problem. Another thing to keep in mind is that you need to modify the data structures that contain the nodes and links of the force layout in place, i.e. you can't set new nodes and links for the force layout and expect everything to work smoothly.
Related
I need to be able to draw links between the circles in a circle pack layout, like {source: i, target: j}. I've seen some questions about how to combine this layout with the force layout that made me think It could be a way to achieve this but I haven't had any luck on that path, also what I need is something completely static. Thank you in advance for any suggestions.
I finally could draw lines between nodes by appending them to the svg and calculating each line position based on the radius of the nodes that each line were to connect, but the problem was that the pack layout that I'm using is zoomable, so when I tried to zoom by clicking the lines neither translate nor re-sized (of course, since there was no code performing such things), so I tried to implement a translation function for the lines so they would move along with the zoom, then I saw that it would take some serious geometry to achieve this, so since I'm a lazy programmer and not at all experienced with d3 I tried to come with something more simple... at last I decided to represent the links between the nodes with a different approach (without lines), I used the "mouseover" event so when the pointer is over a node it will highlight (changed circle stroke attribute color and width) the nodes connected to it. This way I achieved my goal and the view looks a lot cleaner without all the lines crossing over it (they were a lot). I know that some may think that this does not answer the original question, and I'm sure that this can be achieved by someone with more experience (and time and patience) using lines and implementing the right calculation, but in my case this solution solves my problem and maybe it could be of help to others.
I would like to create a force directed graph, but i need it to stay the same every time it is generated (with the same data).
Is there any way to do this using d3.js?
UPDATE:
I found working solution, which is based on using seeded random number generator
// set the random seed
Math.seedrandom('mySeed');
You could by modifying D3's force layout, or by creating your own layout based on it. There are at least 3 places where randomness (Math.Random) is used in the positioning of nodes (there may be more, given the force layout references other code). You would have to eliminate all randomness in order to get the graph to display in the same way each time:
https://github.com/mbostock/d3/blob/master/src/layout/force.js
However, this would hamper how the layout works – it's using randomness to sort itself out into a legible diagram quickly. If your number of nodes is small, then it probably wouldn't be an issue, but a large number of nodes could just end up a tangle.
I'm looking at plotting a scatterplot with a large number of points (500,000 and upwards).
Currently, we're doing this in Python with Matplotlib. It plots the points, and it provides controls to pan and zoom. I don't believe it provides any clustering or points, it just plots them all - doesn't make much sense at the zoomed out view, I suppose, but you can zoom in and they're all there.
I was looking at doing the chart in JavaScript, to make it a bit easier to distribute. I was looking at D3.js, to see if something similar is feasible there. I did find this example of a basic scatterplot:
http://bl.ocks.org/mbostock/3887118
Firstly, would you be able to plot that number of points? (500,000 and upwards) I was under the impression you couldn't due to the overhead of all the DOM objects? Are there ways around this?
Secondly, is there any kind of clustering available, either a library or even just an example of this being done in D3.js?
Thirdly, if anybody knows any good examples of pan/zoom functionality and clustering, or even just a packaged JS library that handles it, that would be awesome.
Fourth, it would be also nice to have click handlers for each point - and to display some text either in a overlay, or even just in a separate window. Any thoughts on this?
Can you draw half a million points with D3? Sure, but not with SVG. You'll have to use canvas (here's a simple example with 10,000 points that includes brush-based selection: http://bl.ocks.org/emeeks/306e64e0d687a4374bcd) and that means that you no longer have individual elements to assign click handlers to. You will not be able to render half a million points with SVG, because all those DOM elements will choke your interface, as you mentioned.
D3 does include quadtree support that can be leveraged for clustering. It's in use in the above example to speed up search but you could use it to nest elements in proximity at certain scales.
Ultimately, your choices are:
1) Some other library/custom implementation that renders in canvas and polls the mouse position to give you the data element rendered at that point.
2) A sophisticated custom D3 approach that nests elements in proximity and only renders SVG elements appropriate at the zoom level and canvas position (pan) you're at.
Yes, D3.js can be made to work with million scale data with two things:
pre-rendering on the server side. For more see here: https://mango-is.com/blog/engineering/pre-render-d3-js-charts-at-server-side/
By aggregating (or clustering) part of the data so that user can interact and expand the graph if need be. For this use collapsible nodes if you can (http://bl.ocks.org/mbostock/1062288).
Also avoid using force layout. It takes time to settle and converge to a stable positioning.
For clustering libraries, I would pick one up off the shelf. I would choose the scikits library from python, there are many in JavaScript but they are not very robust as they mostly cover k-means or hierarchical clustering. I would precalculate the coordinates using scikits by clustering and then render it using D3.
D3 handles Pan and zoom. Again click handlers and text display are available in D3. (http://bl.ocks.org/robschmuecker/7880033)
I'd like to visualize a 20K node dependency graph in d3. Force-directed graphs such as http://bl.ocks.org/mbostock/1153292 are too slow to render in the browser for this number of nodes.
Basically I want to represent nodes containing text and directed edges from one node to another, and add zooming and panning functionality. How can I go about doing this in d3?
Here's an alternative which doesn't seem to use force to lay out the nodes - there's no springing, performs well, and has built in upload/download facility. Its license is MIT/X:
Interactive tool for creating directed graphs using d3.js
directed-graph-creator
Operation:
drag/scroll to translate/zoom the graph
shift-click on graph to create a node
shift-click on a node and then drag to another node to connect them with a directed edge
shift-click on a node to change its title
click on node or edge and press backspace/delete to delete
The zoom behaviour (and pan) you would get basically for free through the zoom behaviour. The layout you would have to do yourself though -- the force layout is pretty much the only thing in D3 you can use to lay out a graph of this kind.
Regardless of what you're using, with 20K nodes anything dynamic is going to be pretty slow -- simply rendering all the elements is going to take quite some time during which the browser will seem unresponsive. An alternative you may want to consider is to pre-render the graph using something more suitable for large amounts of data, save the result as an image (or even static SVG) and add a little bit of D3 code on top for zoom/pan.
I'm using the radial tree example from d3.js (tree-radial.js) and when you click on a node it should move to the center (set it as the new root). I want to get a smooth transition from one tree structure to another but I can't get it to work at all. The click is recognized but I'm not sure how to transition the nodes. Can somebody explain me the steps to get this work or link a short example where this is done?
I don't know if this helps, but you can have a look at this: http://bl.ocks.org/1249394. The clicked node doesn't move to the center in this example, but in essence you will still need to make some similar transitions, just that you will have to adjust the position of the node to be in the center (slightly different coordinates for the transform).